Micro Fluxgate Magnetic Sensor Interface Circuits Using Δ∑ Modulation

Abstract

This paper presents high-resolution micro fluxgate magnetic sensor interface circuits using 2nd-order ΔΣ modulation. The fluxgate sensing element is placed in modulation loop in order to reduce the instability due to the use of ferromagnetic core. As one of the integrators, a continuous-time integrator is used, and that is also used for the anti-aliasing filter for phase sensitive detector output. The oversampling A/D conversion using the 2nd-order ΔΣ modulation is useful for the high-precision detection of extremely weak magnetic field in the order of nanotesla. The interface LSI chip using ΔΣ modulation is designed and fabricated. The magnetic field measurement is successfully performed using the fabricated interface LSI chip and a fluxgate sensing element.